需要帮助了解为啥要从我的所有列表中删除数据

Posted 2023-04-12

【中文标题】需要帮助了解为啥要从我的所有列表中删除数据

【英文标题】：Need help understanding why data is being removed from all my lists需要帮助了解为什么要从我的所有列表中删除数据

【发布时间】：2020-11-21 09:10:45

【问题描述】：

我目前有问题和答案从 .json 文件加载到统一中，然后将此数据放置在未回答的问题列表中，然后当生成新问题时，它会删除当前显示的问题。但是，它也会删除加载信息的数据主列表。下面的代码就是用来做这个的：

    using System.Collections;
    using System.Collections.Generic;
    using UnityEngine;
    using System.IO;
    using UnityEngine.UI;
    
    public class QuestionHandler : MonoBehaviour
    
        [SerializeField] public Text questionText;
        [SerializeField] public Text answerAText;
        [SerializeField] public Text answerBText;
        [SerializeField] public Text answerCText;
    
        [SerializeField]
        private QuestionData _QuestionData = new QuestionData();
        public static List<Question> unansweredQuestions;
        private Question currentQuestion;
        private QuestionData questionData;
    
        public void SaveIntoJson()
        
            string question = JsonUtility.ToJson(_QuestionData, true);
            System.IO.File.WriteAllText(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Desktop) + "/QuestionGameData/QuestionData.json", question);
            Debug.Log(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Desktop) + "/QuestionGameData/QuestionData.json");
        
    
        // Start is called before the first frame update
        void Start()
        
            if(!Directory.Exists(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Desktop) + "/QuestionGameData"))
            
                Directory.CreateDirectory(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Desktop) + "/QuestionGameData");
                File.Create(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Desktop) + "/QuestionGameData/QuestionData.json");
                SaveIntoJson();
            
            Load();
            Debug.Log(_QuestionData.questions[0].questionName);
    
            //if the unansweredQuestion list has no data or all the questions have been removed it will copy in the data from the _QuestionData list
            if (unansweredQuestions == null || unansweredQuestions.Count == 0)
            
                Debug.Log("No questions present loading in saved data");
                unansweredQuestions = _QuestionData.questions;
            
            Debug.Log(unansweredQuestions[0].questionName);
    
            SetCurrentQuestion();
        
    
        // Update is called once per frame
        void Update()
        
            
        
        public void SetCurrentQuestion()
        
            int randomQuestionIndex = Random.Range(0, unansweredQuestions.Count);
            currentQuestion = unansweredQuestions[randomQuestionIndex];
    
            questionText.text = currentQuestion.questionName;
            answerAText.text = currentQuestion.answerA;
            answerBText.text = currentQuestion.answerB;
            answerCText.text = currentQuestion.answerC;
        
    
        public void SetNewCurrentQuestion()
        
            if (unansweredQuestions == null || unansweredQuestions.Count <= 0)
            
                Debug.Log("No more questions left in the list!");
                _QuestionData = questionData;
            
            else
            
                //removes current question from the list so no question comes up twice
                unansweredQuestions.Remove(currentQuestion);
    
                //randomly picks a new question out the remaining questions
                int randomQuestionIndex = Random.Range(0, unansweredQuestions.Count);
                currentQuestion = unansweredQuestions[randomQuestionIndex];
    
                questionText.text = currentQuestion.questionName;
                answerAText.text = currentQuestion.answerA;
                answerBText.text = currentQuestion.answerB;
                answerCText.text = currentQuestion.answerC;
    
                Debug.Log(_QuestionData.questions.Count);
                Debug.Log(unansweredQuestions.Count);
                    
        
    
        void Load()
        
            string filePath = System.IO.Path.Combine(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Desktop) + "/QuestionGameData/QuestionData.json");
            string data = System.IO.File.ReadAllText(filePath);
    
            questionData = JsonUtility.FromJson<QuestionData>(data);
            Debug.Log("Got Data!");
            //sets the loaded questiondata into the game question list
            _QuestionData = questionData;
        
    
        private void OnApplicationQuit()
        
            //SaveIntoJson();
        
    
    
    //format of the questions within the game
    [System.Serializable]
    public class QuestionData
    
        public List<Question> questions = new List<Question>();
    
    
    [System.Serializable]
    public class Question
    
        public string questionName;
        public string answerA;
        public bool isA;
        public string answerB;
        public bool isB;
        public string answerC;
        public bool isC;
    

在左侧显示问题数据的主统一屏幕：

任何理解这一点的帮助都会很棒我已经尝试使用debug.log 来查看发生了什么，但我无法解决。

【参考方案1】：

你在做

unansweredQuestions = _QuestionData.questions;

所以在这一行之后，两个字段都指向同一个列表引用。 =>当您稍后通过

删除问题时

unansweredQuestions.Remove(currentQuestion);

此项目已从 _QuestionData.questions 中删除，因为它是同一个列表。

---

为了避免您应该创建和处理列表的副本，而不是像

unansweredQuestions = new List<Question>(_QuestionData.questions);

---

那么为了节省你可能只想保留unansweredQuestions，除了第一次

public void SaveIntoJson(bool overwriteWithUnanswered = true)

    if(overwriteWithUnanswered) _QuestionData.questions = unansweredQuestions;

    var question = JsonUtility.ToJson(_QuestionData, true);
    System.IO.File.WriteAllText(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Desktop) + "/QuestionGameData/QuestionData.json", question);
    Debug.Log(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Desktop) + "/QuestionGameData/QuestionData.json");

并且只在`Start中第一次传入false

if(!Directory.Exists(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Desktop) + "/QuestionGameData"))

    Directory.CreateDirectory(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Desktop) + "/QuestionGameData");
    File.Create(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Desktop) + "/QuestionGameData/QuestionData.json");
    SaveIntoJson(false);

---

另外两个注意事项：

通常对于文件路径，您应该始终使用 Path.Combine 而不是手动连接 + "/"

您应该存储路径一次，而不是一直一次又一次地获取它

  private readonly string filePath = Path.Combine(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Desktop), "QuestionGameData", "QuestionData.json");

然后简单地在任何地方重复使用它，例如在

public void SaveIntoJson(bool overwriteWithUnanswered = true)

    if(overwriteWithUnanswered) _QuestionData.questions = unansweredQuestions;

    var question = JsonUtility.ToJson(_QuestionData, true);
    Debug.Log(filePath);
    System.IO.File.WriteAllText(filePath, questions);    

【参考方案2】：

因为它是参考副本。创建一个新列表

        //sets the loaded questiondata into the game question list
        _QuestionData.questions  = new List<Question>(questionData);


List<Question> mainlist = new List<Question>();
    List<Question> sublist = new List<Question>();
    Question current;
    [System.Serializable]
    public class Question
    
        public string questionName;
        public string answerA;
        public bool isA;
        public string answerB;
        public bool isB;
        public string answerC;
        public bool isC;
        public override string ToString()
        
            return $"Question  questionName = Answer answerA ";
        
    

    public void Load() 
        mainlist = new List<Question>() 
        
            new Question()questionName="Question A",answerA="A" ,
             new Question()questionName="Question B",answerA="B" ,
              new Question()questionName="Question C",answerA="C" ,
               new Question()questionName="Question D",answerA="D" ,

        ;

        // sublist = mainlist; if you uncommment these you will get the same behavior you have.
        sublist = new List<Question>(mainlist); ///Do these in order to avoid reference problems
    
    public void showList(List<Question> sublist)
    

        foreach (var item in sublist)
        
            Console.WriteLine(item);
        
    
    public void showList()
    

        showList(mainlist);
        showList(sublist);
    
    public void SetCurrentQuestion()
    
        int randomQuestionIndex = new Random().Next(0, mainlist.Count);
        current = mainlist[randomQuestionIndex];

    
    public void Remove()
    
        sublist.Remove(current);
    
    


    static void Main(string[] args)
    
        var p = new Program();
        p.Load();
        p.SetCurrentQuestion();
        p.Remove();
        p.showList();
        Console.WriteLine("Hello World!");